1. Field of the Invention
The present invention relates in general to a microwave oven, and more particularly, to a microwave oven improved in a structure of a cavity casing forming a cooking compartment.
2. Description of the Related Art
FIG. 4 is an exploded perspective view of a conventional microwave oven, and FIG. 5 is a sectional view of FIG. 4, taken along line Vxe2x80x94V, for illustrating the state that a cavity casing is combined to a main casing. As shown therein, a conventional microwave oven 101 comprises a main casing 110 formed with a cooking compartment 121 and a component compartment 122, a cavity casing 120 provided inside the main casing 110, an outer casing 105 having an inverted xe2x80x9cUxe2x80x9d shape and covering the main casing 110 and the cavity casing 120, and a door 107 provided in the front of the main casing 110 and opening/closing an opening 118 of the cooking compartment 121.
The main casing 110 is comprised of a lower plate 111, a front plate 113 standing on the front of the lower plate 111 and provided with the opening 118 having an approximately rectangular shape, a rear plate 115 standing on the rear of the lower plate 111. Inside the main casing 110 is provided the cavity casing 120 forming the cooking compartment 121.
The cavity casing 120 is of an approximately rectangular box shape opened forward and backward, and edges thereof are each provided with flanges 123a and 123b which are bent outwardly. Further, on a bottom of the cooking compartment 121, i.e., on the bottom plate 125 of the cavity casing 120 is provided a tray seating part 131 having a circular shape and recessed downwardly. On the tray seating part 131 is seated a rotatable tray 141 for putting food thereon, and under the center of the tray seating part 131 is provided a driving motor 143 for rotating the rotatable tray 141.
The cavity casing 120 is coupled to the main casing 110 by projection welding in the state that the front flange 123a thereof is in contact with the edge of the opening 118 provided on the front plate 113 of the main casing 110 and the rear flange 123b thereof is in contact with the rear plate 115 of the main casing 110, respectively.
Herein, the projection welding is a kind of a resistance welding. According to the projection welding, a projection part is interposed between two metal workpieces at predetermined intervals, and high electric current is applied to the projection part. Then, heat generated due to resistance of the projection part melts the projection part, so that the melted projection part joins two metal workpices together.
However, according to the conventional microwave oven 101, in order to perform the projection welding for coupling the cavity casing 120 to the front plate 113 and the rear plate 115 of the main casing 110, there is in need of a sufficient space for inserting a welding electrode 150 between the front plate 113 or the rear plate 115 of the main casing 110 and the tray seating part 131 of the cavity casing 120, so that the diameter of the tray seating part 131 should be small in comparison with the width of the cooking compartment 121.
Moreover, according as the diameter of the tray seating part 131 is relatively small, the diameter of the rotatable tray 141 seated on the tray seating part 131 should get small, so that the amount of food accommodated in the microwave oven is also small.
Accordingly, the present invention has been made keeping in mind the above-described shortcomings and user""s need, and an object of the present invention is to provide a microwave oven in which a tray seating part and a rotatable tray are enlarged, securing a sufficient space needed for performing welding work.
This and other objects of the present invention may be accomplished by the provision of a microwave oven comprising a main casing, a cavity casing combined to the main casing so as to form a cooking compartment and having opposite side walls and a bottom plate, and a tray rotatably seated on the bottom plate of the cavity casing, the bottom plate of the cavity casing comprising a tray seating part for seating the tray on the center thereof; and an elevated part protruded upwardly around the tray seating part.
Preferably, between the elevated part and the tray seating part is provided an inclined part.
Preferably, between the elevated part and the each side wall of the cavity casing is provided a recess part.
Preferably, the elevated part forms a pair, being oppositely provided around the tray seating part, and having open parts forward and backward.